Retenção de água em solos de várzea e coxilha sob diferentes usos na região sul do Rio Grande do Sul

Abstract

The importance of soil resources for the proper functioning of the environment becomes increasingly evident. Due to the search for productivity and sustainability in production processes, has researched the quality of the soil and how the use and management practices affecting this. Therefore, this study aimed to evaluate the water retention curve and quantify the maximum storage of water available to plants in soils of upland and lowland areas of a farm in the Southern half of Rio Grande do Sul under different uses. The areas evaluated were upland under forest (CX-MN), upland under native grassland (CX-CN), upland cultivated with soybeans under no-till (CX-S), lowland under forest (VZ-MN) and lowland cultivated in conventional tillage rotation with rice / soybean (VZ-AS). For the study were evaluated particle size, the curve of water retention in the soil and available water storage in the soil layers 0 - 5, 5 - 10, 10 - 15, 15 – 20 and 20 - 30 cm depth. To collect the samples was open a trench 35 cm deep, where distorted samples were collected for particle size analysis, with a repeat for each layer. And for the determination of water retention curves, undisturbed soil samples were collected with the help of volumetric rings 4 cm in height and 5,7 cm in diameter, with 3 replicates per location and layer. In these samples were applied tensions of 10 kPa, 33 kPa, 100 kPa, 500 kPa and 1100 kPa. The difference between field capacity (10 kPa) and permanent wilting point (1100 kPa) was considered as the available water capacity in each treatment. The treatments MN CX, CX CN and MN VZ showed higher water retention in the first layers. The highest values of AD were found in treatments MN CX, CX VZ CN and MN. The lowland area showed the highest PMP that was correlated with particle size. This area has the highest amount of silt and clay, thus presenting with finer texture, compared to area upland. CC water in upland showed no correlation with the texture. The retention curve of soil water becomes important in studies of soil quality, especially in areas under different land uses to analyze its effects on the environment over time.